Membranous nephropathy is a disease in which the small blood vessels in the kidney (glomeruli), which filter wastes from the blood, become inflamed and thickened. As a result, proteins leak from the damaged blood vessels into the urine (proteinuria). For many, the loss of these proteins eventually causes some signs and symptoms known as nephrotic syndrome.
In mild cases, the disease often gets better on its own, without any treatment (remission). As the level of protein leakage increases, so does the risk of long-lasting damage. In many people (as many as 40 percent), the disease ultimately leads to kidney failure. Although there's no cure, treatments are available to slow the progress of the disease.
Membranous nephropathy usually develops gradually, so people often don't notice anything wrong. As you lose more protein from your blood, you may notice swelling in your legs and ankles and weight gain from excess fluid. Some people experience lots of swelling from the very beginning of the disease. Most people do not have any severe symptoms until their kidney disease is advanced. Signs and symptoms include:
When to see a doctor
Until recently, the cause of most cases of membranous nephropathy was not known — termed idiopathic. But recent research has found evidence of autoimmune activity in a majority of cases studied. In autoimmune diseases, such as rheumatoid arthritis or lupus, your body's immune system mistakes some of your own tissues as foreign invaders and attacks them with autoantibodies. These autoantibodies are now thought to be the cause of the damage to the glomeruli in most cases of membranous nephropathy.
Sometimes membranous nephropathy is brought on by other causes, notably:
Factors that can increase your risk of membranous nephropathy include:
Preparing for your appointment
You're likely to start by first seeing your family doctor or a general practitioner. If your doctor suspects you may have a kidney problem, you may be referred to a doctor who specializes in the kidneys (nephrologist).
To prepare for your appointment:
Preparing a list of questions will help you make the most of the time with your doctor. Here are some basic questions to ask:
Tests and diagnosis
The main sign of membranous nephropathy is the loss of protein, primarily albumin, from the blood into the urine (proteinuria). An otherwise healthy person would excrete less than 50 milligrams (one-thousandth of an ounce) of albumin a day in the urine. Someone with membranous nephropathy may excrete several hundred milligrams of albumin a day, up to more than 10 grams (four-tenths of an ounce) with advanced disease.
Tests used to determine the cause of the disease and how well your kidneys are functioning include:
Removing a small piece of your kidney tissue for a pathologist to examine under a microscope (kidney biopsy) is the best way to identify the kind of kidney disease, to see how much damage has occurred and to evaluate the effectiveness of treatment.
Treatments and drugs
Treatment focuses on addressing the cause of your disease and relieving your symptoms. There is no cure.
In cases where the disease is caused by a medication or another disease (such as a tumor), stopping the medication or controlling the other disease will usually improve your condition.
Research has shown that as many as 30 percent of people with membranous nephropathy have a complete resolution of symptoms (remission) over several years without any treatment, and 10 to 30 percent have a partial remission. Doctors generally want to avoid using strong drugs, which have side effects, early in the course of the disease, when there's a chance that the disease will improve on its own.
If your urine protein level remains less than 4 grams a day and creatinine clearance remains normal for a six-month follow-up period, you are considered low risk. Creatinine is a waste product filtered from the blood by the kidney. You have only a small risk of developing serious kidney disease over five years.
Higher protein levels, higher risk
You are considered at moderate risk if your urine protein level stays between 4 and 8 grams a day with creatinine clearance at normal or near normal over six months of observation. About half the people with these symptoms develop serious kidney disease over five years.
You are considered high risk if the protein in your urine is greater than 8 grams a day and persists over the following months or if your kidney function is either below normal or decreases during the observation period. People with these symptoms have a high risk of progressing to serious kidney disease over five years.
If your proteinuria is getting worse, you may be prescribed drugs to suppress your immune system, such as a calcineurin inhibitor, or a combination of corticosteroids with a chemotherapy drug. (Corticosteroids alone rarely work in people with membranous nephropathy.) These drugs are effective in reducing urine protein levels and stopping the progress toward kidney failure. But they have significant side effects, they don't help everyone, and symptoms return for many people after treatment ends. Some of the side effects of chemotherapy drugs — such as risk of bladder cancer, leukemia and infertility — occur long term and may not be noticeable at the time of the treatment.
People who don't respond to a first course of immunosuppression therapy or who relapse may benefit from a second course of treatment.
A drug called rituximab (Rituxan) has shown effectiveness in people who have not benefited from immunosuppressive therapy. The drug kills B cells in the immune system. They are the cells that produce the antibodies that damage the glomeruli. However, use of this drug is still experimental and rituximab is expensive and not generally covered by insurance plans.
Lifestyle and home remedies
Talk to your doctor about how to reduce your chances of developing kidney disease. Your doctor may suggest:
Last Updated: 2011-10-12
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